1. Field of the Invention
The present invention relates to an ink-jet recording head substrate, an ink-jet recording head, and an ink-jet recording apparatus.
2. Description of the Related Art
In an ink-jet recording head, in order to eject a plurality of kinds of ink from one substrate, a plurality of ink supply ports are provided on the one substrate. Additionally, in order to improve the removal performance of ink accumulating on an orifice plate of the one substrate, the substrate is connected to an external instrument by providing electrode pads arranged along sides of the substrate periphery parallel to the shorter side of the groove of each ink supply port. In this configuration, since the distance between an exothermic body and the electrode pad is different regarding the position of the exothermic body, the exothermic body located remote from the electrode pad has been liable to have a large wiring resistance. Accordingly, when a plurality of exothermic bodies connected to one piece of wiring are simultaneously driven from the same electrode pad, the voltage drop in the wiring is increased, so that sufficient electric power does not pervade the exothermic bodies and appropriate bubbles cannot be obtained in comparison with the case that one exothermic body is driven.
Then, as shown in FIG. 7, a configuration in that a line of exothermic bodies is divided into blocks, each block having a plurality of exothermic bodies, and the wiring to an electrode pad is provided for each block so that the wire resistance value for each block is equalized to each other, as disclosed in Japanese Patent Laid-Open No. 10-44416 (corresponding U.S. Pat. No. 6,409,315), for example. In this configuration, by the time-sharing drive in that only one exothermic body is driven within one block at one drive timing, the individual wiring has been achieved in that one exothermic body is driven with one piece of wire at a time.
However, in recent years, there have been demands for ink-jet recording apparatuses that are faster and record with improved image quality. As such, it is necessary for ink-jet recording heads to have more exothermic bodies to be driven with higher frequency. In order to drive a number of exothermic bodies, it is considered to increase the number of time-shared partitions, i.e., the number of exothermic bodies within one block.
By increasing the number of time-shared partitions in such a manner, a number of exothermic bodies can be driven without changing the number of pieces of wiring. However, since a predetermined unit time determined by the frequency is divided into smaller units, a driving time for each exothermic body is reduced. When the exothermic bodies are driven with higher frequency for achieving faster speeds, the driving time is further shortened.
However, in order to stably eject ink, energy applied to each exothermic body needs to be controlled. For this reason, a control technique of changing the driving time has been used. When the driving time of the exothermic body is extremely shortened, a bubble necessary for ejecting ink does not sufficiently grow in the ink, resulting in poor ejection. Accordingly, the driving time of the exothermic body is necessary to some extent, and the driving time is shortened to the limit at present. Therefore, it is difficult to achieve the method as described above.
On the other hand, in order to drive the exothermic body with the same frequency by increasing the number of exothermic bodies without changing the driving time, the number of the exothermic bodies driven at a time is increased, i.e., the number of blocks needs to be increased. In order to drive the exothermic body with higher frequency for achieving the speeding-up, it has been required to reduce the number of time-shared partitions and to increase the number of blocks. With increasing frequency, the driving time of each exothermic body is decreased, so that the minimum driving time is secured by reducing the number of time-shared partitions.
In a conventional wiring method as shown in FIG. 7, the wiring to the electrode pad is individually routed for each block. In order to increase the number of blocks for increasing the number of the exothermic bodies driven at a time, the number of pieces of individual wiring needs to be increased. However, in the individual wiring, the distance from the electrode pad in the substrate periphery to be connected is different regarding the position of the block, so that the length of the wiring is different. Since with increasing length of the wiring, the resistance increases, in order to equalize resistance values by eliminating the wiring resistance differences due to the block position, formerly, the smallest wire in diameter has been used for the block closest to the electrode pad, and with moving distance away from the electrode pad, the wire is increased in diameter. Since the smallest wire diameter has physically a limit, with increasing number of blocks, larger wire in diameter is necessary for the block remote from the electrode pad. As a result, if the number of the exothermic bodies driven at a time is doubled, the wire width increases by three to four times, so that a problem arises that the substrate rapidly increases in size.